1. Field of the Invention
The present invention relates to an apparatus for use in a chemical vapor deposition process and a method for fabricating a semiconductor device. And more particularly, the present invention relates to a gas heating apparatus that previously applies heat to and then activates process gases for the chemical vapor deposition.
2. Description of Related Art
The Chemical Vapor Deposition (CVD) is a process that reaction gases are introduced in a main chamber and then react with one another above a hot substrate to form a thin film, such as a SiO2 insulating film, or a tungsten (W) or aluminum (Al) thin film. In order to increase the efficiency of CVD process, the reaction gases are previously heated and then activated using a gas heating apparatus. Then, such a gas heating apparatus is usually installed in a gas inlet of the main chamber where the chemical vapor deposition (CVD) is performed.
FIG. 1 is a detailed portion cross sectional and partially cutaway view of a gas heating apparatus for the chemical vapor deposition according to a related art.
In FIG. 1, the gas heating apparatus includes a quartz tube 30 that is a reaction-gas passage, a line heater 50 that contacts and surrounds the surface of the quartz tube 30, ceramic balls 40 that are contained inside the quartz tube 30, a chamber frame 10 that is packing the gas heating apparatus, a heat insulating material 20 that is formed on the inside surface of the chamber frame 10, and a coolant passage 11 that is installed in the chamber frame 10 to cool the chamber frame 10.
In the gas heating apparatus of FIG. 1, the reaction gas flows through the quartz tube 30 and then contacts with the ceramic balls 40. Therefore, the reaction gas is activated by the ceramic balls 40 that contain thermal energy generated from the line heater 50. At this point, the reaction gas is introduced in the gas heating apparatus with a high velocity, so that the quartz tube 30 is designed to have a spiral shape like a spring in order to take a sufficient time for the reaction gases to be activated. Substantially, the spiral shape of the quartz tube 30 prolongs the length of the quartz tube 30 within the gas heating apparatus. Further, in order to apply heat to the reaction gas during the reaction gas activation in the gas heating apparatus, the line heater 50 is wound around the surface of spiral-shaped quartz tube 30. And the ceramic balls 40 are located inside the spiral portion of the quartz tube 30.
However, the gas heating apparatus of FIG. 1 has some disadvantages. There is a limitation of prolonging the length of the spiral-shaped quartz tube 30 because, the gas heating apparatus of FIG. 1 becomes too large. Additionally, due to the fact that the quartz tube 30 has a small diameter, a small number of ceramic balls 40 are contained inside the quartz tube 30, and thus the reaction gas is hardly activated. Also it is difficult to embrace the line heater 50 because the line heater 50 is wound around the spiral-shaped quartz tube 30.